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The neuroprotective agent sipatrigine blocks multiple cardiac ion channels and causes triangulation of the ventricular action potential
Author(s) -
Gao Zhan,
Milnes James T,
Choisy Stéphanie C M,
Leach Michael J,
Hancox Jules C,
James Andrew F
Publication year - 2005
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2005.04312.x
Subject(s) - repolarization , chemistry , ic50 , inward rectifier potassium ion channel , pharmacology , patch clamp , ion channel , cardiac action potential , medicine , electrophysiology , endocrinology , biophysics , biology , biochemistry , in vitro , receptor
Summary 1. Sipatrigine (BW 619C89), a blocker of neuronal Na + and Ca 2+ channels that is structurally related to lamotrigine, has been shown to be neuroprotective in models of cortical ischaemia. Although associated with cardiovascular effects in animal models in vivo , there is no published information concerning the effects of sipatrigine on cardiac ion currents and action potentials (AP). 2. The aim of the present study was to examine the effects of sipatrigine on the delayed rectifier currents (I Kr and I Ks ), the inward rectifier current (I K1 ), the L‐type Ca 2+ current (I Ca,L ) and the fast Na + current (I Na ), as well as on AP duration at 30% (APD 30 ) and 90% (APD 90 ) repolarization, in guinea‐pig isolated ventricular myocytes. 3. Each of the currents was inhibited by sipatrigine, demonstrating the drug to be a relatively broad‐spectrum blocker of cation channels in the heart. However, sipatrigine was a comparatively more potent inhibitor of I Kr (IC 50 = 0.85 µmol/L) and I Ks (IC 50 = 0.92 µmol/L) than of I K1 (IC 50 = 5.3 µmol/L), I Ca,L (IC 50 = 6.0 µmol/L) and I Na (IC 50 = 25.5 µmol/L). 4. Consistent with block of I Kr , I Ks and I K1 , sipatrigine (1–30 µmol/L) produced a concentration‐dependent prolongation of APD 90 . Although lower concentrations of sipatrigine (≤ 3 µmol/L) caused APD 30 prolongation, higher concentrations (≥ 10 µmol/L) shortened APD 30 , consistent with an involvement of I Ca,L blockade. The contrasting effects of sipatrigine on APD 30 and APD 90 at higher concentrations resulted in a marked concentration‐dependent triangulation of the AP. 5. The results of the present study demonstrate that sipatrigine, at concentrations previously shown to be neuroprotective in vitro , modulates cardiac K + , Ca 2+ and Na + currents and repolarization of the cardiac ventricular action potential.